Cast-resin transformers of the described type are for example known from the product literature "Technische Information Giessharz-Transformatoren" of Starkstrom-Geratebau GmbH of Regensburg (1985). Such dry transformers are increasingly popular, in particular in the region up to about 600A due to their simpler construction and not the least because of the environmental advantage with respect to clophene- or oil-insulated transformers.
With these transformers the connector conductors and with them the taps of an existing step winding lead to connector tabs on the output coil rails or directly on the core sleeve of the cast-resin winding and there are connected by connection lines with the step switch.
German patent 3,630,415 describes using a conventional oil-filled step switch which is mounted on a support laterally adjacent the transformer and which is connected electrically by connection lines.
Swiss patent 391,088 further describes an arrangement where the connections are extended out of the transformer to contacts which are arranged like a collar around the periphery of a cylindrical housing in which the step switch is recessed so that same is connectable by respective contacts on the outside of the step-switch housing electrically with the collar of contacts and therethrough with the transformer.
Another built-on step switch of the load-selector type for oil transformers is known from German published application 2,712,484 which has a grid that fixes and guides the connection lines between the step contacts and the respective transformer.
Finally a cast-resin transformer is known from Japanese utility model Sho-62-10,973 wherein the connections of the step winding are extended to a cast-in-place contact plate whence they are extended by electrical connector lines to a step switch.
All these known arrangement have substantial disadvantages.
First in every case there are a plurality of electrical connections on the step switch with the respective taps of the transformer by means of numerous electrical lines. This is expensive, requires special means for mechanically fixing these conductors and for avoiding electrical interaction, and does not in addition allow for a change of connectors for example during assembly or repair. It is further disadvantageous that the adjacent step switch must be fixed near the transformer by means of special holders, traverses, struts, or the like that are not normally provided on or needed by the transformer. This means further that the respective step switch must not only be matched in every case to the electrical characteristics of the transformer, its number of steps, and so on, but also to the respective mechanical and constructive circumstances, such as size, type, style, and position of the electrical connections and of the mechanical mounting means and so on.